Happel started his professional playing career at Rapid Wien, where he made his first team debut at age 17. Forming a solid defensive partnership with Max Merkel, he played 14 years for Rapid, from 1943 till 1954 and 1956 till 1959, winning the Austrian Championship title six times. He was chosen in Rapid's Team of the Century in 1999.[1]

Happel made his debut for Austria in September 1947 against Hungary and was a participant at the 1954 FIFA World Cup in Switzerland, where he helped them reach third place, and also at the 1958 World Cup. His last international was a September 1958 match against Yugoslavia. He earned 51 caps and scored 5 goals.[2]

After retiring as a player, Happel went on to become one of the greatest coaches of all-time. He won the league title in four different countries. He also took two different clubs to gold in the European Champions' Cup (now the UEFA Champions League) and the Netherlands to second place in the 1978 World Cup. His first club was ADO Den Haag in 1962, with whom he won the Dutch Cup in 1968. After Den Haag he coached Feyenoord, with whom he won the Dutch championship in 1971, as well as the European Cup and the Intercontinental Cup in 1970.

At the 1978 World Cup in Argentina, Happel was coach of the Dutch national team and reached the final against the Argentine national team. Always a man of few words, Happel's pre-match pep talk is said to have consisted of just one sentence: "Gentlemen, two points." The Dutch, however, lost the final.

All youth players of Rapid Vienna automatically became member of the Hitler Jugend in 1938. Ernst reported he refused to sing along to their songs until he was kicked out of their gatherings.[3]

He was conscripted and dispatched to the Eastern Front in 1943. Although he never saw action, he was arrested by the Americans in 1945. He escaped by jumping out of the train wagon in Munich and took several months to make his way back to Vienna. He smuggled himself into the Russian zone with the excuse that he had seen from afar his house was still standing and that he'd started playing at Rapid Vienna again.[3]

Ernst Happel never married. He was described by one of his ex-players Birger Jensen as a bit of a loner, always accompanied by his cigarettes and cognac.[4] He nevertheless would meet up with Austrian friends, enjoying card games, pool and darts.[4]

A heavy smoker for most of his adult life, Happel died of lung cancer in 1992 at age 66. In the wake of his death, the biggest football stadium in Austria, the Praterstadion in Vienna, was renamed the Ernst-Happel-Stadion. Four days after his death, Austria played against Germany and reached a 0–0 draw; Happel's cap lay on the bench during the entire match.